High Acceptance Spectrometer

The specrometer is divided into 6 sectors surrounding the beam axis covering large angular acceptance between 16 and 88 degrees. HADES is comprised of the following components: A diamond START detector, a Ring Imaging Cherenkov (RICH), four sets of Multiwire Drift Chambers (MDC), a superconducting toroidal magnet and a multiplicity/electron trigger array consisting of granular pre-shower detectors at forward angles and two time of flight walls: a scintillator based time-of-flight wall (TOF) and the RPC wall built from resisitive plate chambers.

Advanced Particle Identification

A major improvement of the spectrometer in terms of granularity and particle identification capability was achieved by installation of new shielded timing Resistive Plate Chamber (RPC) time-of-flight detectors at low polar angles (between 18° and 45°). In beam measurements show an average efficiency of 99%, a time resolution of 73 ps together with an average longitudinal position resolution of 7.7 mm. An efficient and accurate track reconstruction in a high track density environment of Au+Au collisions allows for an excellent particle identification via the momentum versus velocity correlation.

High Precision Event Reconstruction

In Au+Au reactions at 1.25 GeV/u up to 200 charged particles are registered in the HADES acceptance. The tracking system of the spectrometer is capable of handling such an amount of tracks at high rates. Extrapolation of the trajectories backward from the tracking detectors to the target region allows the reconstruction of the primary vertex. HADES uses a 15 segmented target to reduce the conversion probability in the target material. The resolutions of the global vertex fit allows to asign individual reactions to the target segment where the reaction took place.

High Data Quality

The data quality in terms of statistics, mass resolution and particle identifcation allow for precise measurements in various fields of hadron physics.• Systematic studies of e+e- production in nucleon-nucleon and heavy-ion collisions resulting in an isolation of true in-medium effects.• First observation of omega signal in e+e- decay channel at SIS18 energies in proton (see figure) and heavy-ion induced reactions.• Hyperon (Σ(1385) and Λ(1405)) production in proton-proton reactions.• Strangeness production (ϕ, K+/-, Ξ(1321)) in heavy-ion collsions.

High Rate Data Acquisition

The new DAQ system features Field Programmable Gate Array based electronic boards and optical data transmission. An FPGA-based custom network with optical links inside the detector and a commercial Gigabit Ethernet infrastructure transports data to the server farm. The custom optical network features high bandwidth, low latency bi-directional data transport. All data are transported via this network on dedicated virtual channels: trigger information, event data and slow-control information.~7 billion Au+Au events have been recorded in 2012. The mean data rate during the flat top of the extracted beam was 100 MBytes/s at an event rate of 10 kHz. This corresponds to 20% of the peak performance of the DAQ system.

Fair Facility

The future international Facility for Antiproton and Ion Research (FAIR) in Darmstadt will provide unique research opportunities in the fields of nuclear, hadron, atomic and plasma physics. In particular, the available antiproton and ion beams offer the possibility to investigate fundamental aspects in strong interaction physics (QCD).Tell me more

The HADES experiment has been designed to study di-electron emission in heavy ion reactions. However, its powerful particle identification capabilities and excellent momentum resolution also allows precise measurements of hadron properties in elementary collisions. Below we present two recent results, which are cited in the Particle Data Group (PDG 2012).